Bellows mechanism for artificial respiration



Septr- 8, 1959 E. J. RENVALL BELLows MECHANISM FOR ARTIFICIAL REsPIRATIoN Filed oct. 8, 195s.

. 3 Sheets-Sheet 1 lim Hmm WIILIIVII/l Sept. 8, 1959 E, J, RENVALL I 2,902,992

BELLows MEcHANIsM FOR ARTIFICIAL REsPIRAIIoN Filed oct; a, 195e 3 sheets-sheet 2 f /l/l Il' @ml Sept. 8, 1959 E. J. RENVALL 2,902,992

BELLows'MEcHANIsM Fon ARTIFICIAL REsPIRAIIoN Filed oct, a, 195s :s sheets-sheet s INVENTOR, 75m/v frz/r fsm/flu @Erw/SEU United States Patent Ofice 2,902,992. Patented Sept. 8, 1959 BELLOWS MECHANISM FOR ARTIFICIAL RESPIRATIGN Erik Johan Renvall, deceased, late of Lidkoping, Sweden,

by Bengt Gunnar Johan Renvall, administrator, Stocklxolm, Sweden Application October 8, 1956, Serial No. 614,722

Claims priority, application Sweden October 12, 1955 15 Claims. (Cl. I12S- 29) This invention relates to bellows mechanisms for articial respiration.

According to the invention, a bellows mechanism for artificial respiration comprises bellows fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means being provided adjacent the handle for acting on an operating medium which, just before or during the compression stroke of the bellows, is compressed and actuates the valve in the housing to assume a position in which it closes a passage in its housing for exhaled air from the lungs -of a patient and opens a passage for inhalation air, and which, during the return stroke of the bellows, actuates the valve to assume a position in which itV closes the passage for inhalation air and opens the passage for exhaled air.

The invention facilitates rapid closure of the passage for exhaled air from the lungs of the patient.

Theelastic means may be an envelope around the handle of the bellows, the inside of the envelope being connected to the valve housing.

Alternatively, the elastic body may comprise a membrane disposed in a box on a movable end plate for the bellows. The operating handle is movable relative to the movable end plate and is used to compress the bellows by moving the movable end plate towards a fixed end plate. In this case the inside of the box is in cornmunication ywith the valve housing.

In the preferred embodiment of the invention, the bellows are manually operated and consist of two com- -partments separated from each other by a partition, the volume of the compartments being changeable corre- :sponding to the change in volume of the whole bellows. One of these bellows compartments is connected to the passage for inhalation air by a tube and the other compartment is connected to the passage for exhaled air.

The invention will now be more fully described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is .a side elevation of a manually operated bellows mechanism according to the invention,

Fig. 2 is a plan view of the mechanism shown in Fig. 1,

Fig. 3 is an enlarged longitudinal sectional view of the cannula valve, shown in Fig. 1,

Figs. 4 and 5 are diagrammatic views of a modified bellows mechanism according to the invention, showing the bellows during the exhalation and inhalation strokes, respectively,

Fig. 6 is an enlarged side elevation of the upper part of the bellows shown in Figs. 4 and 5,

p Figs. 7 and 8 are diagrammatic views of a two-part bellows mechanism laccording to the invention, showing the bellows during the exhalation and inhalation strokes, respectively.

Referring to Figs. l and 2 bellows 4 are arranged between a fixed end plate 1 and an axially movable end plate 3 which is guided along three columns 2. The columns 2 are parallel to one another and mounted on a base 5. The fixed end plate 1 is secured to the columns 2 in spaced relation to the base 5. Two angle brackets 6 are attached to the movable end plate 3, each bracket being connected to one end of a hollow handle 7 for operating the bellows. In addition, the handle is also attached to the movable end plate 3. A helical compression spring 8 is arranged within the bellows for decompressing them. A valve casing 9 is arranged on the under side of the fixed end plate 1 and a flexible tube 10 connects the casing 9 to a cannula valve 11.

An elongated bulb 12 made of rubber or other elastic material and reinforced with ribs 12a is disposed around the handle 7. The ends 13 of the bulb are sealed to the handle 7. The interior of the bulb 12 is in communication with the interior of the handle by means of holes 14 in the wall of the latter. The handle 7 is open at one end which is connected by a hose 15 to one end of a housing 16 for the cannula valve 11. Fig. l shows the hose 15 passing through the bellows 4 and through the tube 10 to the lvalve housing 16 but this is not essential. It is possible to lead the hose 15 around the bellows and merely fasten it to the outside of the tube 10.

Fig. 3 more clearly illustrates the cannula valve 11 used in the mechanism of Figs. l and 2. A valve, generally indicated at 17, can slide axially within the housing 16 and comprises three valve discs 18, 19, 20 `on a rod 21. The housing 16 has a pipe connection 22 for attaching the hose 15 leading from the handle 7 and a connection 23 for attaching the tube 10 from the bellows 4. The-housing 16 has two further pipe connections or sockets, the one designated 24 serving as an outlet for exhaled air and the one marked 25 being located between the connections 23 and 24 and serving to supply fresh air to the lungs of a patient.

The valve discs 18, 19, 20 are arranged along the rod 21 so that when the valve 17 is in one end position (cxtreme left-hand position as shown in Fig. 3) a free air passage exists between the pipe connections 24 and 25 through the inside of the housing 16, whilst in the other end-position of the valve 17 (extreme right-hand position) the connection 23 is in communication with the connection 25. A suction check valve 26 (Fig. 1) serves to supply fresh air to the bellows 4. A safety valve which is preferably spring operated is arranged in the valve casing 9 or any other suitable position in the mechanism so that it will open if the pressure in the bellows exceeds about 8" of water column.

A stop in the form of a ring 27, is arranged on one of the columns 2 (Figs. l and 2) in order to limit the stroke of the bellows and can be adjusted in height by a clamping screw 28.

The operation of the bellows mechanism is as follows:

After the cannula valve 11 has been applied to the patient, the bulb 12 is gripped by hand and the handle 7 is depressed against the action of the spring 8, causing air to be forced out of the bellows 4 into the tube 10.

The bulb 12, however, is necessarily compressed beforel the bellows 4, and the air within the bulb is forced through theholes `14 and through the interior'of the handle 7 and the hose 15 to act on the valve dise 18 in the housing 16. As a result the valve 17 is quickly moved to the right, and a free air passage is for-med between the connection 23 and the socket 25. The air in the tube 10 is therefore allowed to pass into the lungs of the patient, the compressionstroke of the bellows constituting the inhalation stroke of the mechanism.

After completion of the compression stroke of the bellows, the length ofthe stroke being determined by the position or the stop 27, the bulb 12 is released and the latter is-caused to expand quickly by means of its ribs 12a. The vacuum set up within the bulb 12 as it expands causes the valve 17 to be moved to its starting position (Fig. 3). Such return movement of the valve 17 `can be assisted by a helical spring 29 arranged between the end wall 39 of the housing 16 and the Valve disc 20. Air exhaled by the lungs Vis now free to escape through the connection 25, through the interior of the valve housing 16, and out to atmosphere through the connection 24. At the same time the spring 8 returns the bellows 4 to its initial decompressed position in which the end plate 3 of the bellows abuts against the stop 27, and during expansion of the bellows, fresh air is allowed to enterthrough the suction valve 26.

The most important advantage of the bellows mechanism` thus described is that it works with absolute safety and precision, independently of the pressure applied to press the air into the lungs of the patient. When a small inhalation pressure is used, for instance when giving a child artificial respiration, it can always be ensured that the mechanism will work with absolute safety. lIt is also of great value that the length of the inhalation stroke can 'be varied according to need.

The bellows mechanism can be used for the application of narcosis by providing the bellows or the cannula valve with an additional intake for a narcotic. The cannula valve shown in the drawings may be replaced by some other respiratory valve for insertion vin a face mask. The bulb 12 may be arranged on the handle 7 so that it surrounds only the upper part of the handle. In that case it is possible to operate the bulb without having to pull the handle upwards for expanding the bellows 4 and the spring 8 can be dispensed with.

Referring to the embodiment of the invention Vshown in Figs. 4 6, the end of the housing 16 adjacent the valve disc 18 vcommunicates with a box 35 by means of the hose 15 and a pipe connection 33 at the base 34 of the box. The box 35 is attached to the movable end plate 3 by screws 36 which also secure a cover 37 to the other face of the end plate. The cover 37 is provided with a boss 38 for guiding the rod 39 of an operating handle 40 for the bellows. The lower end of the rod 39 is flanged at 41 and attached to a membrane 43 by rivets 42. The central part of the membrane is clamped.

against the liange 41 by a plate 44. The edge portion of the membrane is clamped between an annular flange 45 -on the box 35 and a ange 46 on the cover 37.

When the handle 40 is pulled upwards (Fig. 4), the bellows are expanded and air is sucked in through the valve 9. A non-return valve 3,1 will then be closed. At the same time the membrane 43 is bent upwards and creates a `vacuum in the box' 35. the valve disc 18 and causes the valve 17 to move to the left. This movement ofy the valve can be assisted b y a helical spring inserted between the valve disc 19 and the right-hand end of the valve housing 16.

In the position of the valve 17 as shown in Fig. 4, exhaled air from the lungs 32 can Vpass through the Valve housing 16 and out through the connection 24. When thehandle 40 is depressed, the membrane 43 will bend downwards (-Fig. and immediately cause the valve 17 to move to Ithe right. The valve disc 19 thereby closes the passage between the lungs andthe pipe 'connection 24 and The vacuum acts on opens the passage between the tube 10 and the connection 25. Upon continued downwards motion ofthe handle the air in the bellows 4 is compressed, the valve 9 being closed. The air pressure opens the valve 31 and air is forced into the lungs 32. After the end of the exhalation stroke inhalation is recommenced as described above.

The end plate 3 may be integral with the box 35 or the cover 37. A compression spring can be inserted in the bellows which, when the handle is released, causes the end plate 3 to return to its starting position automatically. In that case the above mentioned spring for returning the valve 17 to -its left-hand position must be inserted in the housing 16.

According to the 'embodiment of the invention illustrated in Figs. 7 and 8, a partition 47 is attached to the ilexible wall of the bellows 4 to divide it into wvo `cornpartments 48 and 49. A valve housing 16 is included in this bellows mechanism. A valve having a valve disc 19 is movable within the Valve housing 16 by means of the disc 18 in the form of a piston. The valve housing 16 is connected to a cannula or a face mask^(not shown) by means of a -pipe connection orsocket 25. The part of the housing 16 located on one side of the socket 25 (the left-hand side in the drawing) communicates with the part 49 ofthe bellows'by means of a tube 10 connected Vto the end plate 1. A non-return valve 31 from the bellows is located in the upper part of the tube A10.

The part of the valve housing 16 on the other side of the socket 25 (the right-hand side in the` drawings) communicates with the compartment 48 of the bellows by means of a hose 50 which is connected to the partition 47 and which is sealed in an aperture in the end-plate 1. A valve 51 which permits air to pass only from the valve housing 16 is provided in the hose 50 near where it passes the lixed end plate v1. The end plate 1 is provided-with lan inlet valve 9 for fresh air to the bellows and the end plate 3 is provided with a similar valve 52 lfor theescape of exhaled air from the bellows. The end plate 3 is further provided with a safety valve 53 which is adjustable to open at a predetermined vacuum such as 2" of water column, in the compartment 48 of the bellows. The end plate 1 has a similar safety valve 54 which is adjustable to open at a certain positive pressure, such as 8 of water column, in the part 49 of the bellows.

A pressure box 35 having a membrane 43 is arranged on the movable end plate 3. An axially displaceable handle 40 `is attached to thecentral part of the membrane 43. The interior of the pressure box 35 communicates, via a hose 15, with the left-hand end of the valve housing 16. A helical spring (not shown) is 'preferably arranged between, the valve `disc 19 and the right-hand end of the valve housing y16, this spring causing the valve to be urged into the left-hand position shown in Fig. 7.

A ilexible tie arranged between the partition 47 and the end plate 3 (or the box 35) for example a twisted leather cord 55, causes the partition to be moved upwardly when ever the movable end plate 3 is lifted.

The compartments 48 and 49 of the bellows are expanded when the handle 40 is pulled upwards (see Fig. 7*). The piston 18 on the valve rod -21 is thereby caused to move the valve to the left. Thus, a passager 56 between the tube 10 and the pipe socket 25 is closed by the disc 19 and apassage 57 between the `pipe socket 25 and the hose 5t) is opened. Upon further upward movement of the handle 40 the compartments 48, 49 of thebellows are expanded whereby -air is sucked through the valve 9 into the compartment 49 of the bellows and exhaled air is sucked from the lungs 32 of thepatient through the passage 57 and the valve 51 into the compartment 48 of the bellows. This causes the valve 52 to be closed. After this, 'the exhalation stroke, the handle 40 is depressed and the membrane 43 is ilexed downwardly. A positive pressure is thereby obtained within the Ybox 35, causing immediate adjustment of the valve within the housing 16 to assume the position shown` in Fig; 8; In this-position, the passage 57 is closed and-the passage 56 is open. Upon further depression of the handle 40 the end plate 3 and the pantition wall 47 are moved downwardly thereby compressing the air in the compartments 48 and 49 of the bellows. The valves 9 and 51 automatically close and valves 31 and 54 are opened. The air'in the compartment 49 is thereby forced through the passage 56 and lthe cannula into the lungs 32, and the exhaled air in the compantment 48 of the bellows is released through the valve 52. The inhalation stroke is then finished.

A-conduit 58 can be provided beyond the valve 9 (see Fig. 8) for supplying oxygen or narcotics.

lThe bellows mechanism may according to the invention be modified in several ways. Helical springs may be arranged between the end plate 1 and the partition 47 and between the end plate 3 and the partition 47 to facilitate expansion of the compartments 48 and 49 of the bellows as soon as the handle 40 is released upon completion of the inhalation stroke. The handle 40, and thus also the end plate 3, may be reciprocated mechanically, s uch as by an engine.

The invention claimed is:

v l. A bellows mechanism for artificial respiration, comprising bellows fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means being provided adjacent the handle for acting on an operating medium which, just before and during fthe compression stroke of the bellows, is compressed and actuates the valve in the housing to assume a position in which it closes a passage in its housing for exhaled air from the lungs of a patient and opens a passage for inhalation air, and which, during the return stroke of the bellows, actuates the valve to assume a position in which it closes the passage for inhalation air and opens the passage for exhaled air.

2. A bellows mechanism for artificial respiration, comprising bellows fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means comprising an envelope around said handle of the bellows for acting on an operating medium which, just before and during the compression stroke of the bellows, is compressed and actuates the valve in the housing to assume a position in which it closes a passage in its housing for exhaled air from the lungs of a patient and opens a passage for inhalation air, and which, during the return stroke of the bellows, actuates the valve to assume a position in which it closes the passage for inhalation air and opens the passage for exhaled air.

3. A bellows mechanism for artificial respiration, comprising bellows fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means comprising a hollow body located on top of said handle for acting on an operating medium which, just before and during the compression stroke of the bellows, is compressed and actuates the valve in the housing to assume a position in which it closes a passage in its housing for exhaled air from the lungs of a patient and opens a passage for inhalation air, and which, during the return stroke of the bellows, actuates the valve to assume a position in which it closes the passage for inhalation air and opens the passage for exhaled air.

4. A bellows mechanism for artificial respiration, comprising bellows fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means being provided adjacent the handle for acting on an operating medium which, just before and during the compression stroke of the bellows, is compressed and actuates the valve in the housing to assume a position in which it closes a passage in its housing for exhaled air from the lungs of a patient and opens a passage for inhalation air, and which, during the vreturn strke of the bellows, actuates the valve. to,

6 assume a position in which-it closes the passage for vinhalation air and opens the passage for exhaled air, said elastic means being resilient so that it expands after having been compressed and causes the valve to be returned to a position in which the passage for exhaled air is open.

5. A bellows mechanism for artificial respiration, comprising bellows fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means comprising an envelope around said handle of the bellows for acting on an operating medium which, just before and during the compression stroke of the bellows, is compressed and actuates the valve in the housing to assume a position in which it closes a passage in its housing for exhaled air from the lungs of a patient and opens a passage for inhalation air, and which, during the return stroke of the bellows, actuates the valve to assume a position in which it closes the passage for inhalation air and opens the passage for exhaled air, said elastic means being resilient so that it expands after having been compressed and causes the Valve to be yreturned to a position in which the passage for exhaled air is open.

6. A bellows mechanism for artificial respiration, comprising bellows fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means comprising a hollow body located on top of said handle for acting on. an operating medium which, just before and during the compression stroke of the bellows, is compressed and actuates the valve in the housing to assume a position inwhich it closes a passage in its housing for exhaledf. air from the lungs of a patient and opens a passage for inhalation air, and which, `during the return stroke of thebellows, actuates the valve to assume a position in whichy it closes the passage for inhalation air and opens lthe passage for exhaled air, said elastic means being resilient so that -it expands after having been compressed and causes the valve to be returned to a position in which the passage for exhaled air is open.

7. A bellows mechanism for articial respiration, comprising bellows fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means comprising a bulb around the handle the ofuter wall of which bulb being ribbed longitudinally of the handle for acting on an operating medium which, just before and during the compression stroke of the bellows, is compressed and:

actuates the valve in the housing to assume a position in which it 'closes a passage in its housing for exhaled air from the lungs of a patient and opens a passage for inhalation air, and which, during the return stroke of the bellows, actuates the valve to assume a position in which it closes the passage for inhalation air and opens the passage for exhaled air, said elastic means being resilient so that it expands after having 4been compressed and causes the valve to be returned to a position in which the passage for exhaled air is open. 1

8. A bellows mechanism for artificial respiration, comprising bellows fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or vface mask, elastic means being provided adjacent the handle for acting on an operating medium which, just before and during the compression stroke of the bellows, is compressed and actuates' the Valve in the housing to assume a Iposition in which it `closes a passage in its housing for exhaled air from the lungs of a patient and opens a passage for inhalation air, and which, during the return stroke of the bellows, actuates the valve to assume a position in which it closes the passage for inhalation air and opens the passage for exhaled air, said elastic means comprising a membrane arranged in a box on a movable end plate for the bellows, the handle of the bellows being movable with respect to the movable end plate, and adapted to move the-movablei 7 end plate towards a fixed end plate for the bellows, for the purpose of compressing the bellows.

9, A bellows mechanism for artificial respiration, comA prising bellows fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means being provided adjacent the handle for acting on an operating medi-um which, just before and during the compression stroke of the bellows, is compressed and actuates the' valve in the housing to assume a position in which it closes a passage in its` housing for exhaled air from the lungs of a patient and opens a passagefor inhalation air, and which, during the returnstroke of the bel-lows, actuates the valve to assume `a position in which it closes the passage for inhalation air and opens the passage for exhaled air, said elastic means comprising a membrane arranged in a. box on a movable, end plate for the bellows, the handle of the bellows being movable with respect to the movable end plate, and adapted to move the movable end plate towards a fixed end plate for the bellows, for the purpose of compressing the bellows, the central portion of the membrane being attached to the handle and the interior of the box communicating with the valve housing.

10. A bellows mechanism for artificial respiration, comprising bellows tted with a handle for compressing them and connectedV to a valve housing adapted to be attached to a cannula or face mask, elastic means being provided adjacent the handle for acting on an operating medium which, just before and during the compression stroke of the bellows, is compressed and actuates the valve in the housing to assume a position in which it closes a passage in its housing for exhaled air ifrom the lungs of a patient and opens, a passage for inhalation air, and which, during the return stroke of the bellows, actuates the valve to` assume a position in'which it closes the passage for inhalation air and opens the passage for exhaled air, said elastic means comprising a membrane arranged in a box on a movable end plate for the bellows, the handle of the bellows being movable with respect to the movable end plate, and adapted to move the movabie end plate towards axed end plate for the bellows, for the purpose of compressing the bellows, said handle being attached to a rod which is guided in a cover for the box.

11; A bellows mechanism for artificial respiration, comprising bellows fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means being provided;

adjacent the handle for acting on an operating medium which, just before and during the compression stroke ofthe bellows, is compressed and actuates the valve in the housing to assume a position in which it closes a passage in its housing for exhaled air from the lungs of a patient and opens a passage for inhalation air, and which, during the return stroke of the bellows, actuates the valve to assume a position in which it closes the passage for inhalation air `and opensy the passage for exhaled air, said elastic means comprising ay membrane arranged in a box onia movable end plate for the bellows, the handle of the bellows being movable with respect to the movable end plate, and adapted to move the movable end plate towards a fixed end plate for the bellows, for the purpose of compressing the bellows, the central portion of the membrane being attached to the handle and the interior of the box communicating with the valve housing, said handle being attached to a rod which is guided in a cover for the box. j

12. A bellows mechanism for artificial respiration, comprising bellows fitted with a handle for compressing them and connected to a valve housing adapted to `be attached to acannula or face mask, elasticmeans being provided adjacent the handle for acting on an operating mediumwhich, just before and during the compression stroke of the bellows, is compressed and actuates the valve in the housing to assume .a position inwhich it closes a passage in its housing for exhaled air from the lungs of a patient and opens a passage for inhalation air, and which, during the return stroke of the bellows, actuates the valve to assume a position in which i-t closes the passage for inhalation air and opens the passage. for exhaled air, said'bell'ows comprising two compartments separated by a partition the volumes of which being adjustable corresponding to the change in volume of the whole bellowsone of the compartments being connected by a tube to the passage for inhalation air and the other being connected by hose tothe passage for exhaled air.

13. A bellows mechanism for artificial respiration, comprising bellows having fixed and movable end plates- 'and being fitted with a handle for compressing them and connected to avvalve housing adapted to be attached to a cannula or face mask, elastic means being provided adjacent the handle for acting on an operating medium which, just before and during the compression stroke of the bellows, is compressed and actuates the valve in the housing to assume' a position in which it closes a passage in its housing for exhaled air from the lungs of a patient and opens a passage for inhalation air, and which, during the return `stroke of the bellows, actuates the valve to assume aposition in which it closes the passage for inhalation air and opens the passage for exhaled air, said bellows comprising two compartments separated by a partition the volumes of which being adjustable corresponding to the change in volume of the whole bellows one of the compartments being connected by a tube to the passage for inhalation air and the other being connected by hose to the passage for exhaled air, said tube being fastened to the fixed end plate and communicates withv the bellows compartment adjacent the fixed' end plate, said hose being sealed in an apertureL in thel fixed'en'd plate and fastened to the partition to communicate with the bellows Compartment adjacent the movableI end plate.

14. A bellows mechanism for artificial respiration, comprising bellows fitted'with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means being provided adjacent the handle for acting on an operating medium which, just 4before and during the compression stroke ofthe bellows, is compressed and actuates the valve in the housing to assume a position in which it closes a passage in its housing for exhaled air from the lungs of a patient and opens a passage for inhalation air, and which, during the return stroke of the bellows, actuates the valve to assume aposition inl which it closes the passage for inhalation air and opens the passage for exhaled air,

said bellows comprising two compartments separated by a partition the volumes of which being adjustable correspending to the change in volume of the whole bellows one of the compartments being connected by a tube to the passage for inhalation air and the other being connested by hose to the passage for exhaled air, whereas a fiexible tie is arranged between the movable end plate and the partition for returning the partition to its initial position together with the movable end plate at the endl of `an exhalation stroke.

l5. A bellows mechanism for artificial respiration, comprising bellows having fixed and movable end plates and being fitted with a handle for compressing them and connected to a valve housing adapted to be attached to a cannula or face mask, elastic means being provided adjacent the handle for acting on an operating medium which, just before and during the compression stroke of the bellows, is compressed and actuates the valve in the housing to yassume a position in which it closes a passager in its housing for exhaled air from the lungs of a patient and opens a-passageV for inhalation air, and which, during the return stroke of the bellows, actuates the valve to assume a positionl in which it closes the passage for inhalation air and: opens the passage for exhaled air, said bellows comprising two compartments separatedby a partition the volumes of which being adjustable corresponding to the change in volume of the whole bellows one of the compartments being connected by a tube to the passage fou` inhalation air and the other being connected by hose to the passage for exhaled air, said tube being fastened to the xed end plate and communicates with the bellows compartment adjacent the xed end plate, said hose being sealed in an aperture in the fixed end plate and fastened to the partition to communicate (with the bellows compartment adjacent the movable end 10 plate, whereas a flexible tie is arranged between the movable end plate and the partition for returning the partition to its initial position together with the movable end plate at the end of an exhalation stroke.

References Cited in the le of this patent UNITED STATES PATENTS 2,547 Welchman Apr. l1, 1842 1,197,232 Pierpont Sept. 5, 1916 2,737,177 Anklin Mar. 6, 1956 

